Lighting can be used to affect the growth of aquatic animals. Specifically, light is needed for growth of most animal species and substantially affects the animals' behavior in terms of feeding, reproducing, location in the water column, and other factors. Water naturally filters light as the water gets deeper, such that lower light intensity and a different spectrum of light wavelengths reaches deep water.
In aquaculture, carbon dioxide (CO2) and oxides of nitrogen contaminate the water and create an environment that is lethal to certain animals. In nature, algae in the water can consume both CO2 and nitrogen in the course of algae growth and photosynthesis; in so doing, the algae decontaminates the water while providing food to the animals. In order to use algae for such purposes, however, light needs to be present at proper frequencies and intensities to allow the algae to grow using photosynthesis. The quantity of light available in a water pond may be reduced by: 1) less than ideal periods of sunlight being present during a 24 hour solar cycle to permit photosynthesis to take place as may be desired; 2) the reflective nature of the water surface, which reflectance reduces the beneficial effect of available light on photosynthesis, and which reflectance changes as the angle of the sun to the water moves from acute to oblique as the day progresses, thus inhibiting photosynthesis, and 3) the fact that water containing high levels of solids (whether in the form of decaying or living matter, such as decaying or living algae) does not permit light to reach much beyond the surface. When the light in a water pond is reduced, photosynthesis can be reduced or become impossible, and the benefits of photosynthesis may be absent at any depth much below the surface. As such, the use of deeper water levels in aquaculture facilities may prove to be problematic.
Small ponds have several factors which inhibit light penetration into the pond, including lack of wave action, as the smaller body of water is more protected and picks up less wind energy. Without wave action, more light is reflected off of the surface of the water and does not penetrate into the pond (in contrast, with constant wave action, the sun's rays are only reflected a portion of the time and less of the sunlight is reflected as the continuously changing surface does not create a smooth reflective surface). Some measurements estimate that on a smooth surface pond, only 40% of the light energy penetrates the surface of the water. After a certain point, beyond the critical angle, all of the light is reflected off the surface and it becomes dark underwater (although it is still light above the water).
Protection also reduces the clearing of the water surface, and algae or other materials may come to rest on the surface and cloud the surface, which otherwise might have been blown from the surface of the pond and/or dissipated into a larger body of water. The animals may need to have different spectra of light passed to them for different depths of water. For example, a fish whose habitat is within a one meter depth from the surface of a pond may thrive with a different light spectrum than a fish whose habitat is deeper within the pond (e.g., at a depth of 10 meters).
Further, studies have shown that different living organisms are both physiologically and psychologically affected by the wavelength of light they receive. This holds true whether the living organism is a plant or animal as is discussed in several patent applications by the present inventor; including U.S. Patent Publication no. 2015/0150195 entitled “LIGHT SOURCES ADAPTED TO SPECTRAL SENSITIVITY OF PLANTS” and U.S. patent application Ser. No. 14/425,332 entitled “SYMBIOTIC SHRIMP AND ALGAE GROWTH SYSTEM”, both of which are incorporated in full herein.